Image forming apparatus

ABSTRACT

The invention provides an image forming apparatus in which orbit shift can be prevented to perform good image display in an electron beam emitted from the electron-emitting device adjacent to the spacer when an antistatic spacer coated with a high resistance film is used. A surface shape is controlled by forming a fine particle film on the surface of a row directional wiring  5  in which a spacer  3  is arranged, the electron emission is realized from electron-emitting areas  14   a  and  14   b  near contacting areas  15   a  and  15   b  in a non-contacting area  16  in which the spacer  3  is not in contact with the row directional wiring  5,  and the non-contacting area  16  of the spacer  3  is irradiated with the electron to decrease a potential, which allows a good equipotential line  17  to be formed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus which isused as, e.g. a display panel. More particularly, the invention relatesto the image forming apparatus in which a spacer is sandwiched alongwiring between a first substrate, which has plural electron-emittingdevices and the wiring for driving the electron-emitting devices, and asecond substrate, which has an electrode defined at a voltage higherthan that of the wiring.

2. Related Background Art

Generally, in the image forming apparatus in which the first substrateon the electron source side and the second substrate on the displaysurface side are arranged in an opposite manner while separated fromeach other, the spacer made of an insulating and the second substrate inorder to withstand atmospheric pressure. However, the spacer is chargedto affect an electron beam orbit near the spacer, which generates aproblem in that light-emission position is shifted. This causes theimage deterioration such as a decrease in luminance and bleeding inpixels near the spacer.

Conventionally, in order to prevent the charge of the spacer, it isknown that the spacer coated with a high resistance film is used.

Specifically, it is known that the rib-shaped spacer coated with thehigh resistance film is sandwiched along the first-substrate wiring sothat the high resistance film is electrically connected to thefirst-substrate wiring and the second-substrate electrode, or it isknown that a spacer electrode .is provided above and below the spacercoated with the high resistance film and the high resistance film issandwiched between the wiring and the electrode through the spacerelectrode so as to be electrically connected (for example, see JapanesePatent Application Laid-Open No. H8-180821 (U.S. Pat. No. 5,760,538)).

It is also proposed that intermediate layers (spacer electrode) havingthe electrical conductivity are provided on side faces on the firstsubstrate side and second substrate side of the spacer coated with thehigh resistance film respectively and the electron beam orbit iscontrolled by the intermediate layer (spacer electrode) (for example,see Japanese Patent Application Laid-Open No. H10-334834 (U.S. Pat. No.6,184,618)).

However, according to the inventors' study, for the image formingapparatus described in Japanese Patent Application Laid-Open No.H8-180821 in which the high resistance film is electrically connected tothe first-substrate wiring and the second-substrate electrode withoutarranging the spacer electrode, it is newly found that sometimes thecharge of the spacer is not sufficiently eliminated or sometimes thepotential distribution of the spacer surface exhibits the unintentionaldistribution state.

Since the above-described phenomena depend largely on a process ofmanufacturing the display apparatus, the cause of the phenomena is notgeneralized. For example, the unpredictable distortion is generatedbetween the first-substrate wiring and the second-substrate electrode, aforeign matter exists on the first-substrate wiring and thesecond-substrate electrode, and an unintentional burr is generated inthe wring or the electrode. Therefore, the contact is not continuouslyachieved between the high resistance film of the spacer and the wiringor the electrode, and the position in which the high resistance film ofthe spacer is not partially in contact with the wiring or the electrodeis generated, which causes the insufficient electrical contact.Particularly, in the wiring produced by the inexpensive manufacturingmethod, sometimes there is the partial difference in the surface shape,and the electrical contact failure is easy to be generated.

In the above case, not only the charge of the spacer is not sufficientlyeliminated, but also the irregular change is generated in the potentialdistribution of the spacer surface, which results in the problem thatthe electron beam orbit does not corresponds to the design. Further,since the electron beam is accelerated from the first substrate to thesecond substrate, the orbit change emerges more remarkably by deflectionforce on the first substrate side compared with the second substrateside.

Referring to FIG. 10, the electron beam deflection caused by thepotential distribution of the spacer surface on the first substrate sidewill specifically be described.

FIG. 10A shows the potential distribution of the surface of a spacer 3when the high resistance film comes unintentionally into partial contactwith wiring 5 of the first substrate in ranging the thin-plate-shapedspacer 3 coated with the high resistance film along the wiring 5. FIG.10B is an equivalent circuit view of FIG. 10A. The numeral 11 in thedrawing designates a second-substrate electrode, and the numeral 17designates an equipotential line.

As shown in FIGS. 10A and 10B, assuming that resistance between a pointC and a point A is R1, the corresponding resistance between a point Dand the point B becomes R1 at the point B which is of a non-contactingarea, the potential at the point B is increased by voltage dropgenerated by resistance R2 between the point A and the point B, whencompared with the point A. Therefore, the orbit of the electron beamemitted from the electron-emitting device near the point B exhibitsbehavior different from the orbit of the electron emitted from theelectron-emitting device near the point A, which results in thedifference in image (distortion) between the point A and the point B.

On the other hand, for the image forming apparatus also described inJapanese Patent Application Laid-Open No. 8-180821 and Japanese PatentApplication Laid-Open No. 10-334834 in which the spacer electrode isprovided above and below the spacer coated with the high resistance filmand the high resistance film is connected to the first-substrate wiringand the second-substrate electrode through the spacer electrode, anelectric field distribution is generated near an area where the spacerelectrode is exposed to the side face of the spacer. Although theelectric field is substantially even in a lengthwise direction of thespacer (direction parallel to the wiring), the electric field emergesstrongly when compared with the case in which the spacer electrode isnot exposed. Therefore, an arrival position of the electron beamradiated from the adjacent electron-emitting device is easily largelydisturbed due to misalignment in arranging the spacer. It is also foundthat the exposure of the spacer electrode to the side face of the spacecauses the discharge to largely decrease image quality. In order toprevent the large decrease in image quality, it is necessary that thespacer electrode is not exposed to the side face of the spacer, or it isnecessary that the spacer is arranged with high accuracy, which causesthe cost increase.

SUMMARY OF THE INVENTION

In view of the foregoing, an object of the invention is to preventirregular shift of the electron beam emitted from the electron-emittingdevice adjacent to the spacer when the plate-shaped spacer coated withan antistatic high resistance film is used. Another object of theinvention is to suppress the position shift of the arrival position ofthe electron beam emitted from the adjacent electron-emitting deviceeven if the spacer arranging position is slightly shifted. Anotherobject of the invention is to adapt the spacer having the sameconfiguration to various apparatus modes.

In order to achieve the above object, the present invention provides animage forming apparatus comprising:

a face plate which has a luminescent member and an electrode, theluminescent member emitting light by electron irradiation, the electrodebeing defined by a first potential;

a rear plate which has a plurality of electron-emitting devices and aplurality of wirings, the wirings being connected to theelectron-emitting device and defined by a second potential differentfrom the first potential; and

a spacer which is arranged between the wiring and the electrode whilebeing partially in contact with the wiring, the spacer beingelectrically connected to the wiring and the electrode, an end facewhich faces the rear plate having resistivity in the spacer,

wherein an electron-emitting area for emitting an electron onto thespacer is arranged on the wiring in a non-contacting area between thewiring and the spacer in the vicinity of contacting area between thewiring and the spacer.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a structure of a display panel ofan image forming apparatus according to a preferred embodiment of theinvention;

FIGS. 2A and 2B are a partially enlarged schematic view showing thedisplay panel of FIG. 1 and a schematic view showing an abutting surfacebetween a row directional wiring and a spacer;

FIGS. 3A, 3B and 3C are an explanatory view showing an electricalcontact between the spacer and the row directional wiring;

FIGS. 4A and 4B are an explanatory view showing an electrical contactbetween the spacer and the row directional wiring;

FIGS. 5A and 5B are a schematic view showing a structure of a displaypanel of an image forming apparatus according to another preferredembodiment of the invention;

FIGS. 6A and 6B are a schematic view showing a configuration when deviceelectrodes are formed in the same direction in the display panel ofFIGS. 5A and 5B;

FIGS. 7A and 7B are a schematic view showing a configuration when thespacer is not formed in the display panel of FIGS. 5A and 5B;

FIG. 8 is a view for explaining correction of irradiation pointdepending on an initial velocity vector in the display panel of FIGS. 5Aand 5B;

FIGS. 9A and 9B are a view showing the contacting state between thespacer and the row directional wiring according to another embodiment ofthe invention; and

FIGS. 10A and 10B are a view for explaining electron beam deflectiondepending on a potential distribution of a spacer surface in theconventional image forming apparatus.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, the invention will specifically bedescribed.

FIG. 1 is a perspective view showing a structure of a display panel ofan image forming apparatus according to a preferred embodiment of theinvention, and FIG. 1 also shows a part of the structure while cut off.FIG. 2A shows a partially enlarged schematic view of the display panelof FIG. 1, and FIG. 2B shows a schematic view of an abutting surfacebetween row directional wiring and a spacer 3 in FIG. 2A.

As shown in FIG. 1, in the display panel of the embodiment, a rear plate1 which is the first substrate and a face plate 2 which is the secondsubstrate face each other at a predetermined interval, and the inside iskept in vacuum by sandwiching the plate-shaped spacer 3 between the rearplate 1 and the face plate 2 while a periphery is sealed by a side wall4.

An electron source substrate 9 is fixed onto the rear plate 1. Rowdirectional wiring 5, column directional wiring 6, an interlayerinsulating layer 7 (see FIG. 2A), and an electron-emitting device 8 areformed on the electron source substrate 9.

The illustrated electron-emitting device 8 is a surface conductionelectron-emitting device in which an electroconductive thin film havingan electron-emitting region is connected between a pair of deviceelectrodes. The display panel of the embodiment has multi-electron beamsources, in which the surface conduction electron-emitting devices 8 arearranged in an N-by-M matrix M-line and matrix wiring is formed by theM-line row directional wiring 5 and the N-line column directional wiring6. The row directional wiring 5 is located on the column directionalwiring 6 through the interlayer insulating layer 7. A scanning signal isapplied to the row directional wiring 5 through extraction terminals Dx1to Dxm, and a modulation signal (image signal) is applied to the columndirectional wiring 6 through extraction terminals Dy1 to Dyn.

The row directional wiring 5 and the column directional wiring 6 can beformed by applying silver paste by screen printing. It is also possiblethat the row directional wiring 5 and the column directional wiring 6can be formed by photolithography.

In addition to the silver paste, other electroconductive materials canbe used as the material of the row directional wiring 5 and the columndirectional wiring 6. For example, in the case where the row directionalwiring 5 and the column directional wiring 6 is formed by the screenprinting, it is possible to use the application material in which metaland glass paste are mixed. In the case where the row directional wiring5 and the column directional wiring 6 is formed by using the plating todeposit the metal, it is possible to use a plating bath material.

A phosphor film 10 is formed on a lower surface (face opposite the rearplate 1) of a face plate 2. Because the display panel of the embodimentis a color display, three-primary-color phosphors of red (R), green (G),and blue (B) are applied in phosphor film 10 respectively. Each colorphosphor is applied in a stripe shape, and a black conductive material(black strip) is provided between the stripe-shaped phosphors. Thereasons why the black conductive material is provided are as follows.The generation of the shift is prevented in the display color even ifthe irradiating position of the electron beam is slightly shifted, thereflection of the external light is prevented to decrease in displaycontrast, and the phosphor film charge-up caused by the electron beam isprevented. The material mainly containing black lead can be used as theblack conductive material. However, other materials can also be used aslong as the material is applicable to the above purposes. A delta arrayand other arrays can be used as the method of applying thethree-primary-color phosphors in addition to the stripe shape.

A metal back (accelerating electrode) 11 which is the electroconductivemember is provided on the surface of the phosphor film 10. The metalback 11 accelerates and raises the electron emitted from theelectron-emitting device 8. A high voltage is applied from ahigh-voltage terminal Hv to set the metal back 11 at the higherpotential when compared with the row directional wiring 5. In the caseof the display panel in which the surface conduction electron-emittingdevice, usually potential difference ranging from about 5 kV to 20 kV isformed between the row directional wiring 5 and the metal back 11.

The plate-shaped spacer 3 is attached onto the row directional wiring 5while being in parallel with the row directional wiring 5. Both ends ofthe spacer 3 are supported by and attached to blocks fixing spacer 12while the spacer 3 is positioned on the row directional wiring 5. Whenthe spacer 3 is fixed by the blocks fixing spacer 12, kinetic energy ofthe electron is small, which allows the turbulence of the electric fieldto be decreased near the electron-emitting device 8 where the electricfield is easy to affect the electron orbit.

Usually the plural spacers 3 are provided at regular intervals in orderthat the display panel has atmospheric pressure resistance. The spacer 3is sandwiched between the rear plate 1 and the face plate 2. The rearplate 1 has the electron-emitting device 8 and the electron sourcesubstrate 9 in which the row directional wiring 5 and column directionalwiring 6 for driving the electron-emitting device 8 are provided. Thephosphor film 10 and the metal back 11 are provided in the face plate 2.The upper and lower surface of the spacer 3 are in contact with themetal back 11 and the row directional wiring 5 while pressurizedrespectively. The side wall 4 is sandwiched between the peripheries ofthe rear plate 1 and the face plate 2. The connection portion betweenthe rear plate 1 and the side wall 4 and the connection portion betweenthe face plate 2 and the side wall 4 are sealed by frit glassrespectively.

Describing the spacer 3 more detail, the spacer 3 has insulatingproperties for withstanding the high voltage applied between the rowdirectional wiring 5 and the column directional wiring 6 on the rearplate 1 side and the metal back 11 on the face plate 2 side, and thespacer 3 also has the electrical conductivity to such a extent that thecharge is prevented in the surface of the spacer 3. In spacer 3 of theinvention, at least the end face facing the rear plate 1 has theresistivity. As shown in FIG. 5, desirably the spacer 3 is formed by asubstrate 51 made of the insulating material and a high resistance film52 with which the surface of the substrate 51 is coated.

Quartz glass, glass in which a content of impurities such as Na isdecreased, soda lime glass, ceramics such as alumina can be cited as anexample of the material for the substrate 51 of the spacer 3. In thematerial of the substrate 51, it is preferable that thermal expansioncoefficient is similar to or close to the coefficients of the electronsource substrate 9, the rear plate 1, the face plate 2, and the like.

Electric current, in which an accelerating voltage Va applied to themetal back 11 on the high-potential side is divided by a resistancevalue of the high resistance film 52, is passed through the highresistance film 52 with which the surface of the spacer is coated, whichallows the charge to the surface of the spacer 3 to be prevented.Therefore, from the viewpoints of the charge and electrical powerconsumption, the resistance value of the high resistance film 52 is setat a desirable range. From the viewpoint of the charge prevention, it ispreferable that sheet resistance of the high resistance film 52 is 1014Ω/□ or less, it is more preferable that the sheet resistance is 1012 Ω/□or less, and it is the most preferable that the sheet resistance is 1011Ω/□ or less. The lower limit of the sheet resistance of the highresistance film 52 depends on the shape of the spacer 3 and the voltage(potential difference between the row directional wiring 5 and the metalback 11) applied to the spacer 3. In order to suppress the electricalpower consumption, it is preferable that the lower limit of the sheetresistance is 105 Ω/□ or more, and it is more preferable that the sheetresistance of the high resistance film 52 is 107 Ω/□ or less.

While the morphology of the thin film depends on surface energy of thematerial constituting the high resistance film 52, adhesion propertiesto the substrate 51, and temperature of the substrate 51, usually thethin film having thickness of 10 nm or less is formed in an islandshape. In the thin film having thickness of 10 nm or less, theresistance is unstable, and reproducibility is low. On the other hand,when the film thickness is 1 μm or more, film stress becomes large toincrease danger of film peel, and productivity becomes worse because thedeposition time is lengthened. Accordingly, it is preferable that thethickness of the high resistance film 52 formed on the substrate 51ranges from 10 nm to 1 μm, and it is more preferable that the filmthickness ranges from 50 nm to 500 nm. Since the sheet resistance is ρ/t(ρ: specific resistance and t: film thickness), in consideration ofpreferable ranges of the sheet resistance and the film thickness, it ispreferable that the specific resistance ρ of the high resistance film 52ranges from 0.1 to 108 Ωcm. In order to realize the more preferableranges of the sheet resistance and the film thickness, it is preferablethat specific resistance ranges from 102 Ωcm to 106 Ωcm.

For example, metal oxide can be used as the high resistance film 52.Among others, it is preferable that chrome oxide, nickel oxide, andcopper oxide are used as the high resistance film 52. Because thesecondary electron emission efficiency is relatively low in theseoxides, it is difficult that the spacer 3 is charged, even if theelectron emitted from the electron-emitting device 8 hits the spacer 3.In addition to the above metal oxides, carbon is the preferable materialbecause the secondary electron emission efficiency is small.Particularly, because amorphous carbon has high resistance, the propersurface resistance of the spacer 3 is easily obtained when the amorphouscarbon is used as the high resistance film 52.

A nitride of aluminum and a transition metal is preferably used as thehigh resistance film 52. The resistance value can be controlled in thewide ranged from the good conductive material to the insulating materialby adjusting a composition of the transition metal, and the change inresistance value is stably small in the display panel manufacturingprocess. Ti, Cr, and Ta can be cited as an example of the transitionmetal elements.

The nitride films can be formed by the thin-film forming techniquesutilizing a nitrogen gas atmosphere, such as sputtering, electron beamevaporation, ion plating, and ion-assist evaporation. The metal oxidefilm can be formed by the thin-film forming technique utilizing oxygengas atmosphere. In addition, the metal oxide film can also be formed bya CVD method and an alkoxide applying method. The carbon film isproduced by the evaporation, the sputtering, the CVD method, and aplasma CVD method. The amorphous carbon film can be obtained bycontaining hydrogen in the deposition atmosphere or by using hydrocarbongas as the deposition gas.

As described above, the spacer 3 is sandwiched between the rear plate 1and the face plate 2, the high resistance film 52 coating the surface ofthe spacer 3 is in contact with the wiring (row directional wiring 5 inthe embodiment) on the rear plate 1 side and the electroconductivemember (metal back 11 in the embodiment) on the face plate 2 side whilepressurized, and the high resistance film 52 is electrically connectedto the wiring on the rear plate 1 side and the electroconductive memberon the face plate 2 side respectively. As shown in FIG. 2A, because anintersecting portion of the row directional wiring 5 and the columndirectional wiring 6 is projected by the thickness of the columndirectional wiring 6 toward the face plate 2 side from other points, theelectrical connection between the spacer 3 and the row directionalwiring 5 is performed by causing the projected portion to come intocontact with the high resistance film 52. Namely, as shown in FIG. 2B,the electrical connection between the high resistance film 52 and therow directional wiring 5 is performed at the intervals of theintersecting portions such that the intersecting portion of the rowdirectional wiring 5 and the column directional wiring 6 becomes thecontacting areas 15 a and 15 b and other portions except for theintersecting portion become the non-contacting portion 16.

As can be seen from an equipotential line 17 shown in FIG. 2A and FIG.2B, the high resistance film 52 also exists in the non-contacting area16 in the spacer 3, so that the potential of the spacer 3 is raised nearthe non-contacting areas 15 a and 15 b. As described above referring toFIG. 10, in the current paths from the metal back 11 to the contactingareas 15 a and 15 b, since the resistance value of the current paththrough the non-contacting area 16 is larger than that of the currentpath which is not passed through the non-contacting area 16 (forexample, current path from the portion directly above the contactingareas 15 a and 15 b), the potential is raised by the increasedresistance value, which generates the raise in potential of the spacer.

The inventor found that the electron is emitted toward the spacer 3 fromthe row directional wiring 5 in the non-contacting area 16 near thecontacting areas 15 a and 15 b under a certain condition. Namely, theelectron-emitting properties can be added to a part of the rowdirectional wiring 5 by controlling the surface shape of the rowdirectional wiring 5.

Specifically, surface roughness is controlled so as to have anappropriate electric field enhancement factor β. As the electric fieldenhancement factor β is increased, the electron is easy to emit.However, in order to prevent the electron emission in the undesirableportions (except for spacer 3 arrangement position), it is necessary tosuppress the electric field enhancement factor β to a certain degree.Examples of the method of controlling the electric field enhancementfactor β include the method of changing a baking temperature in formingthe row directional wiring 5 by the printing, the method of changing thepaste material, the method of dispersing fine particles in the paste,and the method of applying a fine particle film after the rowdirectional wiring 5 is formed.

Among others, the method of applying the material in which theelectroconductive super-fine particles mainly containing the carbonmaterial, tin oxide, and chrome oxide are dispersed in an organicsolvent is preferable, because the stable surface shape and electricfield enhancement factor β are obtained.

The optimum electric field enhancement factor β is determined by thelater-mentioned “electric field in a steady state.” The electric fieldin the steady state is determined by the accelerating voltage, the shapeof the spacer 3, a physical contacting length between the spacer 3 andthe row directional wiring 5, a gap between the spacer 3 and the rowdirectional wiring 5, the surface state of the row directional wiring 5,and the like. Namely, the value of the electric field enhancement factorβ is selected such that the electron is stably emitted at the desiredposition near the spacer while the electron emission is not performed inother positions.

Thus, since the optimum electric field enhancement factor β isdetermined by the many parameters, it is preferable, though it depends,that the electric field enhancement factor β ranges from about 100 toabout 1000.

The “electrical contact” can be secured in the range wider than thephysical contacting area by the irradiation in the non-contacting area16 near the contacting areas 15 a and 15 b with the electron irradiatedfrom the row directional wiring 5 toward the spacer 3.

Referring to FIGS. 3A to 3C, the above state will be described below.

FIG. 3A shows the potential distribution of the initial state, i.e.before the non-contacting area 16 is irradiated with the electron fromthe row directional wiring 5 toward the spacer 3. In FIG. 3A, thenumeral 17 designates the equipotential line. Then, as shown in FIG. 3B,the electron irradiation is started near the contacting areas 15 a and15 b. In the area irradiated with the electron, since the electronenergy is sufficiently small, the negative charge occurs to decrease thepotential.

In FIG. 3C, the electron emission becomes the steady state, and theelectric field in which the electron narrowly emitted is maintained(steady-state electric field).

As described above, when compared with FIG. 3A in which the electron isnot emitted, in FIG. 3C in which the steady state is obtained as aresult of the electron emission, it is found that the potential isdecreased as if the contacting area is increased.

The equipotential line 17 near the rear plate 1 in the spacer 3according to the invention is schematically shown by a broken line inFIG. 2A. FIG. 2B is a schematic view showing the contact state betweenthe row directional wiring 5 and the spacer 3. The physical contactingarea 15 a is smaller than the physical contacting area 15 b. Thenumerals 14 a and 14 b schematically designate the electron irradiatingarea. The electron irradiating areas 14 a and 14 b are substantiallyequal to each other while the physical contacting area 15 a is differentfrom the physical contacting area 15 b.

It is difficult that the electron-emitting state is actually observed.However, as a result of earnest studies, it is found that the electronirradiating area can be estimated by observing the irradiated spacersurface after the irradiation. Specifically, an impression exists in thephysical contacting area, and a color change area is recognized near theimpression. When the spacer is separately irradiated with an electrongun, the similar color change is observed. Therefore, it is thought thatthe color change near the physical contacting area is caused by theelectron irradiation.

As a result of the further detailed observation of the contacting area,the following features are observed.

FIG. 4A is a schematic view in the case where the physical contactingarea is large, and FIG. 4B is a schematic view in the case where thephysical contacting area is small. In FIGS. 4A and 4B, the numeral 41designates a physical contacting length (impression area), the numeral42 designates an electrical contacting length (color change area), andthe numeral 43 designates a gap length between the spacer 3 and the rowdirectional wiring 5 in the outermost portion of the color change area.When FIGS. 4A and 4B are compared to each other, it is found that FIGS.4A and 4B are substantially similar to each other in the electricalcontacting length 42 and the gap length 43 while the difference existsin the physical contacting length 41. FIGS. 4A and 4B are also similarto each other in the actual arrival position of the electron beam. Theactual arrival position of the electron beam corresponds to the resultof the electron beam simulation assuming that the electrical contactinglength 42 is a potential defining contacting area.

A portion, where the difference exists in the electron beam arrivalposition using the row directional wiring to which the fine particlefilm is not applied, is observed as a comparative experiment. As aresult of the comparative experiment, it is confirmed that thedifference exists in the electrical contacting length 42. Each resultcorresponds to the result of the electron beam simulation assuming thatthe electrical contacting length 42 is a potential defining contactingarea.

Namely, the electron emission toward the spacer 3 from the rowdirectional wiring 5 is controlled in the non-contacting area 16 nearthe contacting areas 15 a and 15 b by the application of the fineparticles, which controls the beam position. In other words, even ifFIGS. 4A and 4B differ from each other in the physical contacting statebetween the spacer 3 and the row directional wiring 5, the substantiallysame state can be realized in the electrical contacting state betweenthe spacer 3 and the row directional wiring 5. Therefore, the control ofthe physical contacting state between the spacer 3 and the rowdirectional wiring 5 can be relaxed.

Thus, at each contacting point, it is found that the good electron beamcontrol can be performed by causing the electrical contacting lengths 42of the FIGS. 4A and 4B to correspond to each other.

It is thought that the electrical contacting length 42 is determined bythe steady-state electric field which is determined by the acceleratingvoltage, the spacer shape, the physical contacting length 41, the gaplength 43, the surface state of the row directional wiring 5, and thelike. However, there are many unclear points yet, and currently thedesign is not achieved using a theoretical computation. However,parameters can experimentally be determined while the color change areais observed.

FIG. 9A shows the mode in which the row directional wiring 5 risesrapidly inside the thickness of the spacer 3 in the state in which thespacer 3 abuts on the row directional wiring 5 when the spacer 3 and therow directional wiring 5 are viewed from the X-direction of FIG. 1. FIG.9B shows the mode in which the bottom surface of the spacer 3 is notflat. Even in the modes shown in FIGS. 9A and 9B, the “electricalcontact” having the variations smaller than those of the physicalcontact can be realized by applying the invention.

As shown in FIGS. 1 and 2, since the pieces of column directional wiring6 are arranged at regular intervals, the contacting areas 15 a and 15 band the non-contacting area 16 are formed at regular intervals. Further,as can be seen from FIG. 1, since the electron-emitting device 8 islocated between the two pieces of row directional wiring 5 and betweenthe two pieces of the column directional wiring 6, all theelectron-emitting devices 8 adjacent to the spacer 3 are located at theposition adjacent to the non-contacting area 16. Therefore, all theelectron beams emitted from the electron-emitting device 8 are evenlyaffected by the surface potential of the spacer 3 corresponding to thenon-contacting area 16.

As schematically shown in FIG. 5B, in device electrodes of theelectron-emitting device 8 of the embodiment, except for the deviceelectrodes adjacent to the spacer 3 (54 b and 55 b, and 54 c and 55 c),the lengthwise directions of the gaps of pairs of device electrodes 54 aand 55 a, and 54 d and 55 d are provided in parallel with the columndirectional wiring 6. In the device electrodes 54 b and 55 b, and 54 cand 55 c of the electron-emitting devices adjacent to the spacer 3, thelengthwise directions of the device electrode gaps are provided with anangle of θ relative to the column directional wiring 6. Like an electronbeam orbit 18 shown by the broken line in FIG. 5A, the electron emittedfrom the electron emitting device flies so as to be separated away fromthe spacer 3 in the electron-emitting portion, the electron flies so asto be brought close to the spacer 3 from the position near the bottomsurface of the spacer 3, and finally the electron arrives at a desiredpredetermined irradiating position 19. FIG. 5A is a sectional view takenon line A5-5A of FIG. 5B. The reasons will be described in detail.

Near Electron-Emitting Portion

As schematically shown in FIG. 5B, the electron emitted with the initialvelocities 57 a to 57 d from the device electrodes 55 a to 55 d havingthe negative potentials toward the device electrodes 54 a to 54 d havingthe positive potentials. In the device electrodes 54 b and 55 b, and 54c and 55 c of the electron-emitting devices adjacent to the spacer 3,the lengthwise directions of the device electrode gaps are provided withthe angle of θ relative to the column directional wiring 6. Therefore,in the electron emitted from the electron-emitting device adjacent tothe spacer 3, because the electrons are emitted with the initialvelocity vectors 57 b and 57 c having components separated from thespacer 3 (Y-direction component), the electrons have the orbit so as tobe separated away from the spacer 3 near the electron-emitting portion.On the other hand, the initial velocity vectors 57 a and 57 d of theelectrons emitted from the electron-emitting devices which are notadjacent to the spacer 3 have the orbit parallel to the spacer 3 becausethe initial velocity vectors 57 a and 57 d have no component separatedaway from the spacer.

FIGS. 6A and 6B show the electron beam orbit 18 and the initial velocityvectors 57 a to 57 d in the case where the device electrodes 54 b and 55b, and 54 c and 55 c of electron-emitting devices adjacent to the spacer3 are provided without the angle of θ (i.e. in the case where theinitial velocity vectors 57 b and 57 c are equal to the initial velocityvectors 57 a and 57 d). FIG. 6A is a sectional view taken on line 6A-6Aof FIG. 6B.

As shown in FIG. 6B, the initial velocity vectors 57 a to 57 d of theelectrons are equal to one another. However, as shown in FIG. 6A, theelectron beam final arrival position is shifted by ΔS toward the spacer3 by a potential distribution 20 formed by the spacer 3.

FIGS. 7A and 7B show the electron beam orbit 18 and the initial velocityvectors 57 a to 57 d in the case where the spacer 3 is removed in thesame device electrode as for FIG. 5. FIG. 7A is a sectional view takenon line 7A-7A′ of FIG. 7B.

Since the initial velocity vectors 57 a and 57 d of the electrons differfrom the initial velocity vectors 57 b and 57 c as shown in FIG. 7B, thefinal arrival positions of the electron beams emitted with the initialvelocity vectors 57 b and 57 c are separated away from an originalpredetermined irradiating position 53 by ΔY.

Referring to FIG. 8, ΔY will be described in detail.

FIG. 8 is a schematic view showing the emitting point and arrival pointof the electron. Starting points of arrows 57 a and 57 b indicate theemitting point, and end points of the arrows 57 a and 57 b indicate thearrival point. FIG. 8 corresponds to the perspective view from the upperside of the face plate 2 through the face plate 2.

The sign L is referred to as curve advancing amount (deflecting amount).The curve advancing amount (deflecting amount) L depends on magnitudesof the initial velocity vectors 57 a and 57 b. When the magnitudes ofthe initial velocity vectors 57 a and 57 b are equal to each other, thecurve advancing amounts L are equal to each other. Namely, when thevoltages applied between the devices are equal to each other, the curveadvancing amount L are substantially equal to each other. Accordingly,the lengths of the arrows 57 a and 57 b of FIG. 8 are equal to eachother. At this point,ΔY=L×sinθThe amount of shift also exists in the X-direction,ΔX=L×(1−cosθ)When θ is sufficiently small, ΔX is sufficiently small with respect toΔY. For example, in the case of θ=10°, ΔX/ΔY is 0.09 or less.

Corresponding Position near Bottom Surface of Spacer 3

As described in FIG. 2, the high resistance film 52 of the spacer 3 isin “electrical contact” with the row directional wiring 5 in eachintersecting portion between the row directional wiring 5 and the columndirectional wiring 6. Therefore, the potential of the non-contactingarea 16 shown in FIG. 2B is raised, as shown in FIG. 5A, theequipotential line 20 having the upwardly convex shape is generated nearthe bottom surface of the spacer 3, and the electron beam 18 flies so asto be brought close to the spacer 3.

As described above, in the electron beam orbit design of the embodiment,it is thought that ΔS generated by the spacer 3 is compensated by ΔY bythe angle of θ.

In the actual design, for example, the angle of θ in which the electronarrives at the predetermined irradiating position 53 and the contactingstate are determined from the static field computation and the electronbeam orbit simulation. It is also possible that the conditions aredetermined based on the measurement data.

EXAMPLE 1

In the display panel described in the embodiment, PD 200 (produced byAsahi Glass Co., Ltd.) is used as the substrate 51 of the spacer 3, andtungsten nitride/germanium nitride compound (WGeN) is deposited as thehigh resistance film 52 by simultaneously sputtering a tungsten targetand a germanium target in nitrogen gas. At this point, deposition isperformed by rotating the substrate 51 of the spacer 3. Therefore, thefilm thickness is 200 nm across the entire surface, and the sheetresistance is 2.5×1012 Ω/□. The thickness of the spacer 3 is set at 300μm, and the height (Z-direction length) is set at 2.4 mm.

A SiO2 layer having the thickness of 0.5 μm is sputtered on the surfaceof the cleaned soda lime glass to form the rear plate 1. The deviceelectrodes of the surface conduction electron-emitting device are formedon the rear plate 1 by the sputtering deposition method and thephotolithography. For the material, Ti having the thickness of 5 nm andNi having the thickness of 100 nm are laminated. The device electrodeinterval is set at 2 μm, and the device electrode angle θ of the deviceadjacent to the spacer 3 is set at 6.1°.

Then, the Ag paste is printed in the predetermined shape and baked at480° C. to form the column directional wiring 6. The column directionalwiring 6 extends to the outside of the electron source forming area toform the pieces of electron source driving wiring Dy1 to Dyn in FIG. 1.The width of the column directional wiring 6 is set at 100 μm, thethickness is set at about 10 μm, and the interval is set at 300 μm.

Then, the paste in which glass binder is mixed into the main content ofPbO is used to form the interlayer insulating layer 7 by the printing.The interlayer insulating layer 7 electrically insulates the rowdirectional wiring 5 from the column directional wiring 6. The thicknessof the interlayer insulating layer 7 is set at about 20 μm.

The row directional wiring 5 is formed on the interlayer insulatinglayer 7 by the same technique as for the column directional wiring 6.The width of the row directional wiring 5 is set at 300 μm, thethickness is set at about 10 μm, and the interval is 920 μm. The rowdirectional wiring 5 is extends to the outside of the electron sourceforming area to form the pieces of electron source driving wiring Dx1 toDxm in FIG. 1.

Then, a Cr film is formed by the sputtering on the rear plate 1 in whichthe device electrodes 54 a to 54 d and 55 a to 55 d are formed, andopenings corresponding to the shapes of the electroconductive thin films56 a to 56 d are formed in the Cr film by the photolithography. Then,solution of organic Pd compound (ccp-4230: produced by OKUNO ChemicalIndustries Co., Ltd.) is applied and baked at 300° C. in atmosphere for12 minutes to form a PdO fine-particle film. Then, the Cr film isremoved by wet etching to form the electroconductive thin films 56 a to56 d having the predetermined shapes by lift-off.

Finally, the fine-particle film is formed on the row directional wiring5. The fine-particle film also functions as the antistatic film, and thefine-particle film is formed over the entire surface of the rear plate1.

The fine oxide particles, in which antimony oxide is doped into tinoxide, are dispersed in a mix solution having a composition ratio of 1:1of ethanol and isopropanol, and the fine oxide particles in the mixsolution is used as the fine-particle film. Mass density of the solidmaterial is set at about 0.1 mass %. A size of the fine particle rangesfrom 5 to 15 nm.

A spray method is used as the applying method. The application isperformed using a spray apparatus on the conditions of a liquid pressureof 0.025 MPa, an air pressure of 1.5 kg/cm2, a substrate-head distanceof 50 mm, and head moving speed of 0.8 m/sec. After the application, thebaking is performed at 380° C. for 10 minutes. The thickness of thefine-particle film is 30 nm, and the sheet resistance is 1010 Ω/□.

In the invention, the material of the fine electroconductive particle isnot limited to the tin oxide. It is also possible that the carbonmaterials, chrome oxide, and the like are preferably used as the fineelectroconductive particle.

In the display panel produced by the above-described manner, when theimage display is performed by setting the voltage applied to the metalback 11 at 15 kV and by setting the voltage applied between the rowdirectional wiring 5 and the column directional wiring 6 at 14 V, thebeam shift (ΔX) in the X-direction is less than a detection limit, andthe good image can be displayed.

When the post-observation of the spacer 3 is performed, the electricalcontacting length 42 estimated from the color change area is about 110μm, and the gap 43 of the outermost portion of the electrical contactinglength 42 of the 110 μm is about 3 μm, while the variations ranging from0 to 100 μm exist in the physical contacting length 41.

According to the invention, “electrical contacting state” is realizedbetween the wiring and the spacer by the electron emitted from theelectron-emitting area on the wiring. Therefore, variations in physicalcontacting state between the wiring and the spacer can be relaxed, andassembly margin between the wiring and the spacer can be increased whilethe position shift of the electron beam arrival position is suppressedto maintain the good display image. Accordingly, the image formingapparatus having the good image display can be provided at a high yield.

This application claims priority from Japanese Patent Application No.2004-191008 filed on Jun. 29, 2004, which is hereby incorporated byreference herein.

1. An image forming apparatus comprising: a face plate which has aluminescent member and an electrode, the luminescent member emittinglight by electron irradiation, the electrode being defined by a firstpotential; a rear plate which has a plurality of electron-emittingdevices and a plurality of wirings, the wirings being connected to theelectron-emitting device and defined by a second potential differentfrom the first potential; and a spacer which is arranged between thewiring and the electrode while being partially in contact with thewiring, the spacer being electrically connected to the wiring and theelectrode, an end face which faces the rear plate having resistivity inthe spacer, wherein an electron-emitting area for emitting an electrononto the spacer is arranged on the wiring in a non-contacting areabetween the wiring and the spacer in the vicinity of contacting areabetween the wiring and the spacer.
 2. The image forming apparatusaccording to claim 1, wherein the electron emission area is made of fineelectroconductive particles located on the wiring.
 3. The image formingapparatus according to claim 2, wherein particle sizes of the fineelectroconductive particles ranges from 5 nm to 15 nm.
 4. The imageforming apparatus according to claim 2, wherein the wiring is mainlymade of silver, and the fine electroconductive particle is made of fineoxide particle in which antimony oxide is doped into tin oxide.
 5. Theimage forming apparatus according to claim 1, wherein the contactingarea between the wiring and the spacer is provided at constant intervalsalong a direction in parallel with the wiring.
 6. The image formingapparatus according to claim 5, wherein the electron-emitting deviceadjacent to the spacer is arranged at a position corresponding to thenon-contacting area between the contacting areas provided at constantintervals, and the electron-emitting device adjacent to the spacer emitsthe electron with an initial velocity vector different from that of theelectron-emitting device which is not adjacent to the spacer.